1. Field of the Invention
The present invention relates to a piezoelectric resonator and to a piezoelectric oscillator having exterior substrates which are laminated over and under a piezoelectric resonating element, and more particularly, the present invention relates to a piezoelectric resonator and a piezoelectric oscillator for use in, for example, a clock generation oscillator for a microcomputer.
2. Description of the Related Art
In the past, piezoelectric resonators constructed by combining a piezoelectric resonating element with a capacitor and built-in load capacitance type piezoelectric oscillators have been proposed. For example, in Japanese Patent No. 2666295, piezoelectric components shown in FIGS. 9A and 9B are disclosed. In a piezoelectric component 101, exterior substrates 103 and 104 are laminated over and under, respectively, a plate-like piezoelectric resonating element 102. The piezoelectric resonating element 102 which includes a piezoelectric diaphragm 105 and excitation electrodes 106 and 107 is an energy-trap type piezoelectric resonator. The excitation electrodes 106 and 107 are arranged to face each other via the piezoelectric diaphragm 105. The excitation electrode 106 is led to one end surface of a laminate body which includes the piezoelectric diaphragm 105 and the exterior substrates 103 and 104. An external electrode 108 is provided on the end surface. The excitation electrode 107 is led to the other end surface of the laminated body and is electrically connected to an external electrode 109 provided on the other end surface.
The external electrodes 108 and 109 are arranged to cover not only end surfaces of the laminated body but also the top surface, a pair of side surfaces, and the bottom surface thereof. In the middle of the laminated body, an external electrode 110 is wound around the bottom surface, the pair of the side surfaces, and the bottom surface thereof.
In the piezoelectric component 101, capacitors are provided between the external electrodes 108 and 110 and between the external electrodes 109 and 110.
The capacitors achieve a high capacitance by using the upper and lower exterior substrates 103 and 104.
In Japanese Patent No. 2839092, Japanese Unexamined Patent Application Publication No. 4-192709, Japanese Unexamined Utility Model Patent Application No. 5-18120, etc., there are disclosed capped piezoelectric components constructed by bonding the piezoelectric resonating element to a package substrate in which a capacitor is provided thereon and then bonding cap material for enclosing the piezoelectric resonating element.
In these capped piezoelectric components, the package substrate which has the piezoelectric resonating element mounted thereon includes a multilayer substrate. In the multilayer substrate, the capacitor is provided. That is, by providing the capacitor in the package substrate, the piezoelectric component constructed by combining the piezoelectric resonating element with the capacitor is miniaturized.
In the piezoelectric component 101 disclosed in Japanese Patent No. 2666295, capacitors connected to the piezoelectric resonating element 102 are configured by arranging each of the exterior substrates 103 and 104 over and under, respectively, the piezoelectric resonating element 102. Accordingly, a piezoelectric component having a reduced height is provided.
When a capacitor having high capacitance is desired, ceramic substrates having a high dielectric constant must be used as the exterior substrates 103 and 104. Such ceramic substrates have a low deflective strength and are difficult to construct as thin walls. Accordingly, each of the exterior substrates 103 and 104 must be thickened to some extent. This prevents the capacitor from having high capacitance.
When a construction is desired in which the exterior substrates 103 and 104, each of which includes a high dielectric constant ceramic substrate, are laminated over and under, respectively, the piezoelectric resonating element, the laminated body is affixed on an adhesive sheet and then is cut. However, when the laminated body is cut, chipping tends to occur because a high dielectric constant ceramic substrate has reduced workability.
That is, in a construction, such as that of the piezoelectric component 101 in which the exterior substrates 103 and 104 are laminated over and under, respectively, the piezoelectric resonating element 102, a low dielectric constant dielectric ceramic substrate which has excellent workability must be used as one of the upper and lower exterior substrates 103 and 104. This prevents the capacitor from having high capacitance.
On the other hand, in the above-described capped piezoelectric component, a cap such as a metal cap is bonded to the top surface of the package substrate. Since the package substrate has a larger planar shape than the cap itself, miniaturization of the piezoelectric component is difficult. In addition, the capacitor cannot be constructed in the cap, and it is constructed exclusively in the package substrate. Therefore, it is difficult to construct the capacitor having high capacitance. Since the capacitor must be constructed exclusively in the package substrate, the dimensions of the package substrate must be increased in this respect as well.
To overcome the above-described problems, preferred embodiments of the present invention provide a piezoelectric resonator having exterior substrates which are laminated over and under a piezoelectric resonating element. The resonator solves the above-described problems such that the resonator is miniaturized and shortened, and a capacitor having high capacitance is achieved.
Further, preferred embodiments of the present invention provide a built-in load capacitance type piezoelectric oscillator in which a three-terminal capacitor is connected to the piezoelectric resonating element that is miniaturized and shortened, so as to provide a capacitor having very high capacitance with no disadvantages.
To this end, according to a first preferred embodiment of the present invention, a piezoelectric resonator includes a piezoelectric resonating element, and a first exterior substrate and a second exterior substrate, laminated over and under, respectively, the piezoelectric resonating element. In the piezoelectric resonator, the first exterior substrate and the second exterior substrate each include a multilayer substrate having at least one layer of an internal electrode.
In the piezoelectric resonator, each of the first exterior substrate and the second exterior substrate have a first internal electrode and a second internal electrode provided via a substrate material layer, and have a capacitor provided therein.
The first exterior substrate and the second exterior substrate each include a pair of a first internal electrode and a second internal electrode provided at the same height level, and a third internal electrode provided with the first and second internal electrodes via a substrate material layer. In the piezoelectric resonator, the capacitors are provided between the first internal electrode and the third internal electrode and between the second internal electrode and the third internal electrode, respectively.
In the piezoelectric resonator, alternatively, the first internal electrode of the first exterior substrate and the first internal electrode of the second exterior substrate are connected to a first electric potential and a second electric potential, respectively, and the second internal electrodes of the first exterior substrate and the second exterior substrate are each grounded.
In the piezoelectric resonator, the first exterior substrate and the second exterior substrate each include a first substrate material layer which is liquid-sintered and a second substrate material layer which is not sintered at the sintering temperature of the first substrate material layer.
According to a second preferred embodiment of the present invention, a piezoelectric oscillator is provided including a built-in load capacitance type piezoelectric oscillator having a plate-like piezoelectric resonating element, and a first exterior substrate and a second exterior substrate which are laminated over and under, respectively, the plate-like piezoelectric resonating element, and which constitutes a three-terminal capacitor connected to the plate-like piezoelectric resonating element. In the piezoelectric oscillator, the first exterior substrate and the second exterior substrate each include a multilayer substrate having at least one layer of an internal electrode.
The piezoelectric oscillator further includes an input electrode, an output electrode, and a ground electrode provided on the surface of a laminate body constructed by laminating the plate-like piezoelectric resonating element, the first exterior substrate, and the second exterior substrate. In the piezoelectric oscillator, the input electrode, the output electrode, and the ground electrode are connected to the corresponding terminals of the three-terminal capacitor constituted by the first exterior substrate and the second exterior substrate.
In the piezoelectric oscillator, the first exterior substrate and the second exterior substrate each include a pair of a first internal electrode and a second internal electrode provided at the same level, and a third internal electrode provided with the first and second internal electrodes via a substrate material layer. The first internal electrode, the second internal electrode, and the third electrode are connected to the input electrode, the output electrode, and the ground electrode, respectively.
In the piezoelectric oscillator, the first exterior substrate includes a first internal electrode connected to the input electrode, and a second internal electrode which is provided with the first internal electrode via a substrate material layer and which is connected to the ground electrode, and the second exterior substrate includes a third internal electrode connected to the output electrode, and a fourth internal electrode which is provided with the third internal electrode via a substrate material layer and which is connected to the ground electrode.
In the piezoelectric oscillator, no electrode is provided on the top surface of each of the exterior substrate.
In the piezoelectric oscillator, the first exterior substrate and the second exterior substrate each include a first substrate material layer which is liquid-sintered, and a second substrate material layer which is not sintered at the sintering temperature of the first substrate material layer.
Other features, elements, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments with reference to the attached drawings.